Systemic Immune-Inflammation Index and Perioperative Risk Scores: A Cross-Sectional Analysis in Elective Surgical...

The systemic immune-inflammation index (SII) (SII = platelet count × neutrophil count/lymphocyte count) is an emerging inflammatory biomarker. We examined correlations between preoperative SII, medication count as a marker of multimorbidity, and established perioperative risk scores in patients undergoing elective noncardiac surgery. This cross-sectional study included 300 adults undergoing elective surgery. SII was calculated from preoperative blood counts. We assessed correlations between SII and clinical variables using Spearman's rank correlation coefficient, including American Society of Anesthesiologists Physical Status Classification System, Revised Cardiac Risk Index (RCRI), Surgical Outcome Risk Tool (SORT) mortality, and medication count. We investigated polypharmacy (≥ 4 medications) as a multimorbidity indicator. Multivariable regression identified predictors of elevated SII (≥ 754 × 10^9 cells/L). This study examined associations only. Mean age was 63.5 ± 9.6 years, 50.7% male. Median SII was 633 × 10^9/L. SII showed weak correlations with RCRI (ρ = 0.15, P = 0.008) and SORT (ρ = 0.12, P = 0.033). The strongest correlation was with medication count (ρ = 0.77, P < 0.001), reflecting multimorbidity burden. In the analysis, polypharmacy (odds ratio [OR], 6.82; 95% CI, 2.05-22.7), higher SORT mortality (OR, 1.69 per 1% increase), and RCRI (OR, 1.48 per point) predicted elevated SII. This cross-sectional association study found weak correlations between SII and risk scores. The strong association with polypharmacy suggests that both measures capture the multimorbidity burden, raising the question of whether SII offers advantages over counting medications. Prospective studies with actual perioperative outcomes are required before SII can be recommended for clinical risk stratification.